DUAL SOLAR ENERGY CONVERSION
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/391 ,539 filed June 26, 2002 and U.S. Provisional Application No. 60/424,070 filed November 7, 2002. The entire disclosures of the aforementioned applications are incorporated herein by reference.
FIELD OF THE INVENTION [0002] The present invention relates to producing useful power from renewable energy sources and, more particularly, to the conversion of solar radiation into useful power.
BACKGROUND OF THE INVENTION [0003] Photovoltaic devices are well known in the art for converting solar energy into electric power. However, only a small portion of the sun's total spectrum is available to perform photovoltaic activity. The remainder of the sun's spectrum primarily produces heat. Further, the photovoltaic process itself generates heat, which reduces the efficiency of photovoltaic modules.
Thus, only limited amounts of useful power can be produced from solar energy via photovoltaic devices, as a substantial portion of solar radiation is received in the form of heat energy. [0004] As recognized by the inventor hereof, means are needed for increasing the amount of useful power that can be generated from solar radiation, including from both solar light and heat energy.
SUMMARY OF THE INVENTION [0005] The present invention provides, among other things, devices and methods for converting solar light and heat energy into useable power (e.g., mechanical and/or electric power). A preferred embodiment of a solar energy conversion device constructed according to the principles of this invention includes at least one photovoltaic module and at least one thermoelectric module thermally coupled to the photovoltaic module. In one preferred embodiment, the photovoltaic module is configured for conducting heat to the thermoelectric module to produce a temperature differential across the thermoelectric module, and the thermoelectric module is configured to produce electric power in response to the temperature differential. Preferably, the photovoltaic module includes opposite first and second sides, the photovoltaic module's first side is adapted for receiving solar radiation, and the photovoltaic module's second side is thermally coupled to the thermoelectric module. The solar energy conversion device may also include a lens positioned over at least a portion of the photovoltaic module's first side for focusing solar radiation thereon.
[0006] A preferred embodiment of a solar energy conversion system constructed according to the principles of this invention includes a thermoelectric/photovoltaic solar collector for producing electric power from solar light and heat energy, and at least a first vapor cycle thermally coupled to the solar collector. Further, the solar collector is preferably configured for transferring heat to a low-boiling-point (LBP) liquid in the first vapor cycle for vaporizing the LBP liquid and cooling the solar collector.
[0007] A preferred embodiment of an electrolysis device constructed according to the principles of this invention includes at least one anode and a plurality of cathodes disposed about and spaced from the anode. Preferably, the anode has a plurality of sides and one of the cathodes is disposed adjacent to each side of the anode. Further, the plurality of cathodes may be arranged in a checkerboard configuration relative to a plurality of anodes.
[0008] These and other features and advantages of the invention will be in part apparent, and in part pointed out below.
BRIEF DESCRIPTION OF THE DRAWINGS [0009] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
[0010] Fig. 1 is a block diagram of a solar energy conversion device according to one preferred embodiment of the present invention;
[0011] Fig. 2 is a block diagram of a solar energy conversion device according to another preferred embodiment of the invention;
[0012] Fig. 3 is a block diagram of a solar energy conversion system employing a vapor power cycle according to another preferred embodiment of the invention;
[0013] Fig. 4 is a block diagram of a solar energy conversion system employing multiple vapor power cycles and internal heat rejection according to another preferred embodiment of the invention;
[0014] Fig. 5 is a block diagram of a system similar to that of Fig. 4 but having a combustor for providing auxiliary heat to power the vapor power cycles according to another preferred embodiment of the invention;
[0015] Fig. 6A is a top view of an electrolysis device according to another preferred embodiment of the invention;
[0016] Fig. 6B is a side view of the device of Fig. 6A; and
[0017] Fig. 6C illustrates a preferred electrode geometry for the device of Fig. 6A.
[0018] Corresponding reference numerals indicate corresponding features throughout the several views of the drawings.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0019] The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
[0020] A first embodiment of a solar energy conversion device constructed according to the principles of the invention is shown in Fig. 1 and indicated generally with reference numeral 20. As shown therein, the device 20 includes a photovoltaic module 22 thermally coupled to a thermoelectric module 24. In operation, a portion of solar radiation 26 impinging on the photovoltaic module 22 is converted by the module into dc current for output via an electrical terminal 28. Additionally, solar heat energy which is conducted through the photovoltaic module 22, and/or heat energy generated by the photovoltaic module 22, is used to induce a temperature differential across the thermoelectric module 24. In response to the temperature
differential, the thermoelectric module 24 produces a dc current for output via an electrical terminal 30. In this manner, the device 20 can produce useable power (i.e., electric power) from both solar light energy and heat energy.
[0021] As shown in Fig. 1 , the photovoltaic module 22 preferably contacts the thermoelectric module 24 with the photovoltaic module positioned on a top side of the thermoelectric module 24. Alternatively, other arrangements can be employed. Additionally, in order to maintain a temperature differential across the thermoelectric module 24, the module 24 preferably rejects heat 32 from a bottom side thereof, as shown in Fig. 1. [0022] The device 20 may optionally include a lens 34 (shown in phantom in Fig. 1 ), such as a Fresnel lens, positioned over at least a portion of the photovoltaic module 22 for focusing solar radiation thereon.
[0023] Fig. 2 illustrates another embodiment of a solar energy conversion device 50 constructed according to the principles of the present invention. As shown therein, the device 50 includes multiple layers 52 of thermoelectric materials bonded to an upper side of a thermally conductive plate 54, and multiple layers 56 of photovoltaic materials bonded over the layers 52 of thermoelectric materials. The thermally conductive plate 54 is coupled to a fluid passage 58 through which a low-boiling-point (LBP) liquid 60 (e.g., a refrigerant), which serves as a heat transfer medium, can flow.
[0024] In operation, solar radiation 62 strikes a top surface of the device 50 and a DC electrical current 64 is generated via photovoltaic activity within the photovoltaic layers 56. Heat 66 produced by the solar radiation 62 conducts through the photovoltaic layers 56, through the thermoelectric layers 52, and through the thermally conductive plate 54 and provides the heat of
vaporization needed to evaporate the incoming LBP liquid 60. In this manner, high pressure outgoing vapor 68 is produced. A portion of the heat that conducts through the layers 52 of thermoelectric materials is converted to electricity via the Seebeck effect and a DC electrical current 70 is generated thermoelectrically.
[0025] Fig. 3 illustrates a solar energy conversion system 100 constructed according to the principles of the present invention in which heat rejection is performed via vaporization of a LBP liquid. As shown in Fig. 3, the system 100 includes a thermoelectric/photovoltaic solar collector 102, such as the device 50 shown in Fig. 2, for producing electric power 104 from both solar light and heat energy, and a vapor cycle 106 thermally coupled to the solar collector 102. The thermoelectric/photovoltaic solar collector 102 is configured for transferring heat to a LBP liquid 108 in the vapor cycle 106 for vaporizing the LBP liquid. [0026] In operation, the LBP liquid in liquid phase 108 is preferably pressurized via a liquid pump 110 into the solar collector 102. Heat produced by solar radiation 112 conducts through the solar collector producing DC electric current 104 while providing the heat of vaporization needed to evaporate the LBP liquid 108. Evaporation of the LBP liquid 108 removes heat from the solar collector 102, and high pressure vapor 114 is formed.
[0027] The high pressure vapor 114 preferably drives an energy conversion device 116 such as a turbine or power piston for producing useful work, and the vapor is allowed to expand to lower pressure. The reduced pressure vapor 118 is then provided to a condenser 120 where the vapor is condensed to the liquid phase via heat rejection to atmospheric air. The liquid
phase LBP liquid 108 is then pumped from the condenser 120 back to the solar collector 102 to repeat the closed Rankine power cycle. In this manner, power is preferably produced in three ways: (i) photovoltaic power generation via light energy converted to DC electrical current 104, (ii) thermoelectric power generation via heat energy converted to DC electrical current 104, and (iii) mechanical power generation via high pressure vapor driving of a suitable energy conversion device (which mechanical power can be further converted to electric power, if desired).
[0028] As noted above, the energy conversion device 116 shown in Fig. 3 may be, for example, a turbine or a power piston. Suitable turbines include a rotary vane turbine of the type disclosed in U.S. Provisional Application No. 60/360,421 filed March 1 , 2002, the entire disclosure of which is incorporated herein by reference, a Tesla turbine, and a jet turbine (i.e., a turbine which utilizes jet propulsion for rotation, and which may or may not be bladeless). Exemplary jet turbines are disclosed in applicant's U.S. Provisional Application No. 60/397,445 filed July 22, 2002, U.S. Provisional Application No. 60/400,870 filed August 5, 2002, U.S. Provisional Application No. 60/410,441 filed September 16, 2002, and U.S. Provisional Application No. [insert no. here] filed December 10, 2002 [and entitled "Drum Jet Turbine with Counter-Rotating Ring Method of Manufacture"], the entire disclosures of which are incorporated herein by reference. Suitable power pistons for use in the present invention includes those disclosed in US Application No. 09/873,983 filed June 4, 2001 , U.S. Provisional Application No. 60/384,788 filed June 3, 2002, and U.S. Application No. 10/454,366 filed June 3, 2003, the entire disclosures of which are incorporated herein by reference.
[0029] Rather than circulating a LBP liquid 108 to be vaporized through the solar collector 102 as shown in Fig. 2, an additional heat transfer medium can be employed to transfer heat from a solar collector to a LBP liquid of a vapor power cycle, as described below with reference to the embodiment of Fig. 4.
[0030] Fig. 4 illustrates another embodiment of a solar energy conversion system 200 constructed according to the principles of the present invention. As shown therein, a photovoltaic/thermoelectric solar collector 202 heats a low-boiling-point-liquid in a power cycle while simultaneously generating electricity thermoelectrically and via photovoltaic cells. Specifically, a liquid phase LBP liquid 204 is withdrawn from a condenser/reservoir 206 via a liquid pump 208. The low-boiling-point-liquid 204 passes through a throttle 210 and into a heat exchange vaporizer 212 where it counter flows a heat transfer medium 214 heated by the solar collector 202. The LBP liquid 204 is vaporized by the heat input from the heat transfer medium 214 within the heat exchange vaporizer 212 and is transformed into high-pressure vapor 216 that is provided through a throttle 218 to a turbine 220. The turbine 220 is driven by the high pressure vapor 216 and is preferably connected to a generator 222 that generates AC current 224. After passing through the turbine 220, the vapor has lower pressure and temperature and returns to the reservoir/condenser 206 where it is bubbled beneath cold liquid phase LBP liquid 204, causing the vapor to condense back to the liquid phase.
[0031] A liquid pump 226 circulates the heat transfer medium 214, such as glycol, from the solar collector 202 and through the heat exchange
vaporizer 212 where heat is given off from the hot liquid 214 to the low- boiling-point-liquid 202 that is vaporized in the high pressure vaporizer 212 to provide the needed latent heat of vaporization in order to vaporize the liquid to high pressure vapor, as noted above. [0032] After passing through the vaporizer 212, the liquid 214 is partially cooled, and then passes through a low pressure vaporizer 228 to vaporize additional low-boiling-point-liquid 204 at a lower pressure and temperature, which further cools the liquid 214 that returns to the solar collector 202 in order to be reheated by solar radiation in a cycle. [0033] The solar collector 202 also generates DC electrical current
230 via its photovoltaic cells and thermoelectric modules from which heat is removed via the circulating liquid 214, thus causing the photovoltaic cells to perform better while also sustaining heat flow through the thermoelectric modules. The DC current 230 passes through electrical lines to an electrolysis unit 232 that uses the DC current to electrolyze water 234 into hydrogen and oxygen for storage in a hydrogen and oxygen battery 236. Suitable batteries include those disclosed in U.S. Application No. 09/774,110 filed January 31 , 2001 , the entire disclosure of which is incorporated herein by reference. [0034] A portion of the AC electrical current 224 generated by the generator 222 may pass through a rectifier 238 for conversion to DC current that may also be used by the electrolysis unit 232 to generate additional hydrogen and oxygen, such that an adequate supply of hydrogen and oxygen is ensured.
[0035] During periods when the sun does not provide sufficient energy, AC current may be produced by the hydrogen and oxygen battery
236, which generates DC current that can be converted to AC current by a rectifier 240. Thus, a continuous supply of AC current is produced by the solar energy conversion system 200.
[0036] Additional liquid phase low-boiling-point-liquid 204 is withdrawn from the condenser / reservoir 206 via the liquid pump 208 and passes through a throttle 242 and into the low pressure heat exchange vaporizer 228 where it counter flows warm liquid 214 produced by the solar collector 202. The LBP liquid 204 is vaporized into low pressure and temperature vapor 244 by the heat input from the warm liquid 214 within the heat exchange vaporizer 228. The low pressure and temperature vapor 244 is then provided to a turbine 246, which is driven by the low pressure vapor, and which is connected to a compressor 248. After passing through the turbine 246, the vapor has lower pressure and temperature and returns to the reservoir / condenser 206 where it is bubbled beneath cold liquid phase low- boiling-point-liquid 204, causing the vapor to condense to the liquid phase.
[0037] Additional liquid phase low-boiling-point-liquid 204is withdrawn from the condenser / reservoir via the liquid pump 208 and passes through a throttle 250 and into a condenser / vaporizer 252 where it counter flows a vapor mixture 254 of refrigerant 256 and pressure equaling gas 258 that provides heat for the vaporization of the low-boiling-point-liquid 204. The refrigerant 256 is condensed to the liquid phase within the condenser / vaporizer 252 due to the temperature decrease and due to pressurization, increase in pressure, provided by the compressor 248. The vapor 260 returns
to the reservoir / condenser 206 and is bubbled beneath cold liquid phase low-boiling-point-liquid 204, causing the vapor 260 to condense to the liquid phase.
[0038] To create a partial pressure refrigeration cycle, the pressure equalizing gas 258, such as ammonia, is bubbled beneath the liquid phase refrigerant 256, such as butane, and the refrigerant 256 is evaporated into a vapor within an evaporator 262. The pressure equalizing gas and refrigerant vapor mixture 254 are withdrawn from the evaporator 262 via the compressor 248 and are compressed into the evaporator / condenser 252 that causes the refrigerant 256 to return to the liquid phase due to lowering of the temperature of the refrigerant by the condenser 252, which evaporates a second refrigerant 204 within the evaporator / condenser 252, as the pressure of the refrigerant 256 is increased by the compressor 248. The pressure equalizing gas 258 is not liquefied by the process as a lower temperature and greater pressure would be required in order to liquefy the pressure equalizing gas.
[0039] The liquid refrigerant 256 and pressure equalizing gas 258 are separated within a separator unit 264. The liquid refrigerant 256 sinks to the bottom of the separator 264 as the pressure equaling gas 258 rises above the liquid refrigerant. The liquid refrigerant 256 flows through a throttle 266 and back into the evaporator 262 beneath liquid refrigerant at the bottom of the evaporator. The pressure equalizing gas flows through a throttle 268 and is again bubbled beneath the refrigerant 256 to lower the partial pressure of the refrigerant 256, causing the refrigerant to evaporate to repeat the refrigeration cycle.
[0040] The low-boiling-point-liquid within the reservoir / condenser 206 is continuously cooled and maintained in the liquid state by the cooling effect of the evaporator 262 located within the center of the reservoir / condenser 206. The cooling effect of the evaporator 262 provides an internal artificial low temperature reservoir to condense the low-boiling-point-liquid 204 back to the liquid phase within the reservoir / condenser 206.
[0041] Alternatively, one or more selective membranes may be used in order to separate the refrigerant 256 and pressure equalizing gas 258, as disclosed in U.S. Provisional Application No. 60/384,126 filed May 30, 2002 and U.S. Application No. 10/441 ,245 filed May 19, 2003, the entire disclosures of which are incorporated herein by reference. Further, absorptive cooling may also be used to separate the refrigerant 256 and pressure equalizing gas 258, as disclosed in U.S. Provisional Application No. 60/381 ,075 filed May 14, 2002 and U.S. Application No. 10/438,801 filed May 14, 2003, the entire disclosures of which are incorporated herein by reference.
[0042] Fig. 5 illustrates another embodiment of a solar energy conversion system 300 constructed according to the principles of the present invention. The system 300 of Fig. 5 is similar to that of Fig. 4, except that the hydrogen and oxygen battery 236 of Fig. 4 is replaced with a hydrogen storage vessel 270 and a combustor 272. During periods when insufficient solar energy is available, the combustor 272 can be used to burn hydrogen stored in the storage vessel 270 (or, alternatively, another combustible fuel) to provide heat for powering the LBP liquid vapor cycles. In this manner, a continuous supply of AC current can be produced by the system 300 of Fig. 5.
[0043] Figs. 6A-6C illustrate an electrolysis device 400 for electrolysis of water into hydrogen and oxygen. As shown therein, the device 400 includes an array of multi-sided anodes 402 and multi-sided cathodes 404 such that each anode 402 is positioned adjacent to several cathodes 404, and each cathode 404 is positioned adjacent to several anodes 402. As a result, electrolysis can be performed on multiple sides of each anode and cathode.
[0044] Preferably, each anode and each cathode has four sides, as best shown in Figs. 6A and 6C, and the anodes are arranged in a checkerboard configuration relative to the cathodes. In this manner, electrolysis can be performed on all four sides of each anode and each cathode (except those positioned about the perimeter of the device). In other words, within the middle of the electrolysis cell arrangement, each anode 402 is surrounded by four cathodes 404 such that a given anode is parallel and immediately adjacent to each of the four cathodes surrounding the anode. [0045] Gaps 406 separate the cathodes from the anodes on all four sides, with a preferred spacing of not less than 1mm and not greater than 5mm. The minimum spacing ensures each anode and adjacent cathodes do not electrically short out, and the maximum spacing is to avoid a spacing that is too great for a pulsed electrical charge to be able to pass through the dielectric effect of substantially pure water being electrolyzed. The most preferred spacing is approximately 2mm.
[0046] In operation, a pulsed positive electrical charge 408 is provided to the anode and a pulsed negative charge 410 is provided to the cathode from a DC current supply or an AC current supply that has been rectified to a DC current supply.
[0047] The electrolysis device 400 preferably includes a sealed housing 412 that is partially filled with a supply of substantially pure water 414 with the water preferably fully covering the electrodes. The proper water level can be maintained by an on/off water control switch 416. The pulsed DC current causes electrolysis of the pure water into hydrogen and oxygen that is contained within the sealed housing 412 and the hydrogen and oxygen are allowed to develop pressure within the housing. Upon sufficient pressure, a supply 418 of hydrogen and oxygen may be extracted from the housing of the electrolysis device 400. [0048] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.